Part 4: Lecture on Urban Bees

Good morning, everyone. Today we're continuing our series on urban ecology by looking at a group of organisms that might surprise you: bees. When we think of bees, we often picture rural landscapes, wildflower meadows, or large-scale agriculture. But in recent years, research has revealed that cities can support surprisingly diverse and abundant bee populations. In fact, some studies have found higher bee species richness in urban areas than in surrounding farmland. So why is this, and what does it mean for how we design our cities? Let's start by considering the resources bees need. Like all animals, they require food, nesting sites, and suitable conditions for survival and reproduction. In rural areas, intensive agriculture has led to what's known as a 'green desert' - vast monocultures that offer little forage for bees except during brief flowering periods. Cities, on the other hand, often contain a mosaic of gardens, parks, cemeteries, railway verges, and even derelict land, which can provide a continuous supply of flowers from early spring to late autumn. This seasonal food supply is critical because many bee species have flight periods that extend beyond the short bloom of a single crop. However, urban environments are highly fragmented. Buildings, roads, and other infrastructure create barriers that can isolate bee populations. This is where the concept of habitat corridors comes in. A habitat corridor is a strip of natural or semi-natural habitat that connects larger patches, allowing organisms to move between them. In cities, these corridors might be linear features like greenways, canal towpaths, or even rows of street trees. Research has shown that bees are more likely to colonise and persist in urban green spaces that are connected by such corridors. Without them, populations can become inbred and vulnerable to local extinction. One of the most exciting developments in urban bee conservation is the use of green roofs. A green roof is essentially a layer of vegetation planted on top of a building. They can range from simple sedum mats to complex ecosystems with wildflowers, grasses, and even shrubs. For bees, green roofs can act as 'stepping stones' in the urban landscape, providing food and nesting opportunities high above the street level. A study in London found that green roofs supported a number of rare bee species, including some that are normally associated with coastal habitats. The key is to use a variety of native plant species and to ensure the substrate is deep enough to allow for ground-nesting bees. Now, let's talk about a major threat to bees in all environments: pesticides. In cities, pesticides are used in parks, gardens, and on road verges to control weeds and insect pests. Neonicotinoids, in particular, have been implicated in bee declines. These systemic insecticides are absorbed by plants and can contaminate nectar and pollen. Even at sub-lethal doses, they can impair bees' navigation, foraging behaviour, and immune systems. Many cities are now adopting pesticide reduction policies, especially on public land. Some are even banning the use of neonicotinoids entirely. But enforcement can be difficult, and there's still a lot of work to do in educating private gardeners about alternatives. Another important aspect is nesting habitat. About 70% of bee species are solitary and nest in the ground, often in bare, well-drained soil. Others nest in hollow stems or dead wood. In cities, these features are often considered untidy and are removed. But leaving some areas of bare ground, or installing 'bee hotels' - bundles of hollow tubes - can provide crucial nesting sites. Interestingly, some bees have adapted to nest in man-made structures, like crumbling mortar in old walls. So, a bit of benign neglect can actually be beneficial. We can't discuss urban bees without mentioning the role of citizen science. Because bees are so widespread and relatively easy to observe, they're ideal subjects for public participation in research. Projects like the 'Great British Bee Count' or 'Bumble Bee Watch' in North America have generated vast amounts of data on bee distribution, abundance, and phenology. This data is invaluable for tracking population trends and identifying important urban habitats. For example, citizen science data from London revealed that the city's population of the buff-tailed bumblebee has increased over the past decade, possibly due to the warming climate and the abundance of winter-flowering plants in gardens. So, what are the planning implications of all this? If we want to create bee-friendly cities, we need to think beyond individual gardens and consider the landscape as a whole. This means incorporating green infrastructure into urban planning from the outset. New developments should include a network of interconnected green spaces, with a diversity of flowering plants and nesting habitats. Green roofs and living walls should be encouraged through building regulations. And pesticide use should be minimised through integrated pest management strategies. Some cities, like Toronto and Berlin, have already adopted pollinator strategies that guide planning decisions. Of course, there are challenges. Space is at a premium in cities, and there are competing demands for land use. There can also be conflicts with other urban wildlife, or concerns about stinging insects in public places. But with careful design and public education, these issues can be managed. For instance, planting bee-attractive flowers away from high-traffic areas can reduce the risk of negative encounters. And it's worth remembering that honeybees, which are the most likely to sting, are just one of many species. Most urban bees are solitary and non-aggressive. To sum up, cities are not just concrete jungles; they can be vital refuges for bees and other pollinators. By understanding their needs - for continuous food supplies, connected habitats, safe nesting sites, and freedom from harmful chemicals - we can design urban environments that benefit both people and wildlife. The evidence from citizen science and ecological research is clear: with the right planning, our cities can buzz with life. Thank you, and I'm happy to take questions now.